The typical wing design for an aircraft includes a primary wing surface, having a leading edge and a trailing edge, with a control surface located on the leading and trailing edges of the wing. Flaps and ailerons are both examples of control surfaces, with flaps being designed to increase wing lift and ailerons used for roll axis control. The flaps on each wing operate in unison to increase wing lift by increasing the camber of the wing. By comparison, ailerons are pivoted oppositely to increase lift on one wing while reducing lift on the opposite wing to induce a rolling moment. Similarly, the elevator sections of the horizon tail are pivotably attached to the fixed tail section to vary lift and provide pitch control.
When either the flap or the aileron is activated, the control surface rotates relative to the trailing edge of the wing. Control surfaces are typically rigid structures which maintain their shape throughout rotation. Therefore, gaps or abrupt changes occur at the hinge area of a conventional control surface. This gap increases the drag and lowers the efficiency of the control surface. Additionally, as the control surfaces are rotated, gaps are formed between the ends of the hinged control surface and the adjacent portions of the fixed wing.
U.S. Pat. No. 5,222,699, issued on Jun. 29, 1993, to Albach, et al., and assigned to the assignee of the present invention discloses a variable control aircraft control surface. This patent discloses the use of an elastomeric transition section between inboard and outboard edges of a variable contour control surface and a main wing portion. The transition sections include thick elastomeric layers with oversized holes therein and rods positioned in the oversized holes. Some of the rods are attached to the main wing portion while others-of the rods are attached to the control surface.
Several wing structures have been designed which provide for variable camber in an attempt to eliminate the need for separate and distinct control surfaces located at the trailing edge of the wing, which in turn would eliminate the abrupt changes or gaps between the separate control surfaces and the trailing edge of the wing. For example, U.S. Pat. No. 2,979,287 to Ross discloses an inflatable wing with variable camber. The design incorporates an inflatable fabric airfoil having upper and lower surfaces tied together by a plurality of tie threads. The flexible fabric forming the body of the wing is made so that the warp cords extend lengthwise or longitudinally of the wing, with the weft cords extending transversely of the wing. The weft cords are made more elastic or resilient than the warp cords so that by varying the inflation pressure inside the wing, the camber of the wing can be changed together with the effective lift-drag ratio.
U.S. Pat. No. 3,118,639 to Kiceniuk discloses a control and propulsion fluid foil. This design provides a foil construction which utilizes fluid pressure applied within cells contained in the foil construction in a manner to cause the foil to warp. This warping changes the amount of lift force acting on the foil, permitting it to function as a control surface. The application of the variable pressures to a series of cells can also produce an undulating motion. This undulation can function as a propulsion means if the foil were used underwater.
An example of a unique wing reinforcement structure is seen in U.S. Pat. No. 2,973,170 to Rodman which provides lightweight reinforcement on the inner surface of the wing and a smooth porcelainized outer wing surface. The reinforcement comprises a network of crossed wires or rods of relatively small diameter. Where the rods cross one another, the cross rods are flattened against the wing so that the reinforcement is in contact with the wing substantially up to the intersection of the wires or rods.
A need exists for an improved aircraft wing structure providing a control surface that allows for variable camber of the wing while eliminating any gap or abrupt change between the trailing edge of the wing and the joining edges of the control surface. Such a device should also provide an uninterrupted upper boundary wing surface and be durable enough to withstand the conditions encountered during flight.